The present invention relates to a titanium hydroxide, photocatalyst obtainable from the titanium hydroxide and a coating agent comprising the titanium hydroxide.
It has been researched that organic materials in water or NOx in air is decomposed and removed by a photocatalytic activity of photocatalyst such as a specific titanium oxide. In these days, it has been attracting an attention of researchers to decompose and remove such things using visible light as a light source in the point of general purpose and usage and it has been desired to develop a photocatalyst which exhibits a superior photocatalytic activity by irradiation of visible light.
Heretofore, the titanium oxide which can be used as a photocatalyst has been produced by calcining a titanium hydroxide, which may be commercially available. However, there are problems such that the photocatalyst obtained by calcining the commercially available titanium hydroxide does not show a sufficiently high photocatalytic activity by irradiation of visible light.
Objects of the present invention are to provide a titanium hydroxide, which may be suitable as a raw material for producing a titanium oxide which exhibits a sufficiently high photocatalytic activity by irradiation of visible light, and to provide a coating agent comprising the titanium hydroxide. Other objects of the present invention are to provide a photocatalyst obtainable from the titanium hydroxide and to provide a simple process for producing a titanium oxide which is suitable for photocatalyst usage.
The present inventors have undertaken extensive studies on a raw material for such a titanium oxide which is suitable for photocatalyst usage, and have completed the present invention.
Thus, the present invention provides a titanium hydroxide having:
(i) a primary differential spectrum of radial structure function obtained from an extended X-ray absorption fine structure spectrum of titanium K absorption edge, the primary differential spectrum having two or more maximal intensities and two or more minimal intensities at interatomic distances in the range of from 1.4 xc3x85 to 2.8 xc3x85, at least two maximal intensities being at an interatomic distance of from 1.4 xc3x85 to 1.7 xc3x85 and at an interatomic distance of from 2.2 xc3x85 to 2.5 xc3x85, respectively, and at least two minimal intensities being at an interatomic distance of from 1.9 xc3x85 to 2.2 xc3x85 and at the interatomic distance of from 2.5 xc3x85 to 2.8 xc3x85, respectively; and
(ii) index X calculated by the equation:
X=(U2xe2x88x92L2)/(U1xe2x88x92L1) 
of about 0.06 or more, wherein U1 and U2 represent the maximal-intensity values at the interatomic distance of from 1.4 xc3x85 to 1.7 xc3x85 and at the interatomic distance of from 2.2 xc3x85 to 2.5 xc3x85, respectively, and L1 and L2 represent the minimal-intensity values at the interatomic distance of from 1.9 xc3x85 to 2.2 xc3x85 and at the interatomic distance of from 2.5 xc3x85 to 2.8 xc3x85, respectively, of the primary differential spectrum.
In addition, the present invention provides a coating agent comprising the above-mentioned titanium hydroxide and a solvent.
Furthermore, the present invention provides a photocatalyst obtainable from the above-mentioned titanium hydroxide and a process for producing the photocatalyst by calcining the titanium hydroxide or subjecting the titanium hydroxide to a hydrothermal treatment in the presence of a solvent.